This research project is designed to investigate the anatomical and physiological differences in the skeletal muscle microcirculation between rats that develop hypertension spontaneously (SHR) and control rats. Utilizing techniques developed for the correlation of the number, length, diameter and flow velocity of each individual segment of the microcirculation and on-line measurement of tissue oxygen tension, tissue pH, systemic arterial pressure, central venous pressure, respiration and heart rate, the dissimilarities in microvascular morphology and reactivity will be established. An assessment will then be made as to the effectiveness of various anti-hypertensive agents in eliminating the vascular differences. Efforts will be directed toward the restoration of microvascular function without compromising other important capillary responsibilities, such as: fluid balance, diffusion pathways, etc.